Method for determining the remaining capacity of a lithium-sulfur battery and battery pack implementing the method

Abstract

The present invention provides a method of determining the remaining capacity of a lithium-sulfur battery using a voltage drop value obtained by applying a constant current in an open circuit state, and a battery pack implementing the same.

Description

TECHNICAL FIELD

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2020-0136625, filed on October 21, 2020, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a method of determining a remaining capacity of a lithium-sulfur battery and a battery pack implementing the same. BACKGROUND

[0003] In recent years, as portable electronic devices, electric vehicles, and large-capacity energy storage systems are developed, a demand for large-capacity batteries is emerging. A lithium-sulfur battery is a secondary battery that uses a sulfur-based material having an S-S bond (sulfur-sulfur bond) as a positive active material and uses lithium metal as a negative active material, and has an advantage in that sulfur, which is a main material of the positive active material, is abundant, non-toxic, and has a low atomic weight.

[0004] The theoretical discharge capacity of a lithium-sulfur battery is 1672 mAh / g-sulfur, and the theoretical energy density is 2600 Wh / kg, and the theoretical energy density of a lithium-sulfur battery is much higher than that of other battery systems that are currently being researched, and thus is attracting attention as a battery having a high energy density characteristic.

[0005] A typical lithium-sulfur battery includes an anode (negative electrode) formed of lithium metal or a lithium metal alloy and a cathode (positive electrode) formed of elemental sulfur or other electroactive sulfur materials.

[0006] Sulfur at the cathode of a lithium-sulfur battery is reduced in two stages upon discharge. In the first stage, sulfur (e.g., elemental sulfur) is reduced to lithium polysulfides (Li2S8, Li2S6, Li2S5, Li2S4). These species are mostly soluble in the electrolyte solution. In the second stage, lithium polysulfides are reduced to Li2S that can deposit on the surface of the anode. Conversely, during charging, Li2S is oxidized to lithium polysulfides (Li2S8, Li2S6, Li2S5, Li2S4), and then to lithium and sulfur.

[0007] When the remaining capacity (SOC) of a lithium-sulfur battery is 70%, lithium polysulfide shows a maximum value, and thereafter, it decreases. According to this mechanism, when the remaining capacity (SOC) is 70%, the electrochemical reaction of a lithium-sulfur battery changes, and as shown in FIG. 1, the OCV or operating voltage of a lithium-sulfur battery and the remaining capacity are not proportional to each other. Figure 1

[0008] Therefore, unlike a typical lithium-ion battery in which the remaining capacity is determined only by measuring the voltage because the voltage continuously decreases according to the amount of discharge, a lithium-sulfur battery has a characteristic in which the remaining capacity cannot be reliably determined only by measuring the voltage when the remaining capacity is less than 70%.​

[0009] As conventional techniques for solving these problems, there are known methods such as deriving internal resistance by introducing composite modeling and monitoring changes in electrolyte properties using optical methods.

[0010] However, under the conventional techniques described above, the methods for estimating remaining capacity not only appear complex, but also lack sufficient accuracy.

[0011] [Existing Technical Documents]

[0012] [Patent Documents]

[0013] Korean Patent Publication No. 10-2018-0041149 Summary of the Invention

[0014] [Technical Issues]

[0015] The present invention is conceived to solve the problems of the prior art described above. Therefore, the object of the present invention is to provide a method for determining the remaining capacity of a lithium-sulfur battery and a battery pack implementing the method, which can reliably determine the remaining capacity in a lithium-sulfur battery in a simple manner.

[0016] [Technical Solution]

[0017] In order to achieve the above goals,

[0018] This invention provides a method for determining the remaining capacity of a lithium-sulfur battery, comprising the following steps:

[0019] a) After applying a constant current to the battery in an open-circuit state, measure the initial voltage drop dV at any point within the range of 0.01 to 0.3 seconds;

[0020] b) After applying a constant current, measure the subsequent voltage drop dV2 at any point within the range of 0.5 seconds to 20 seconds;

[0021] c) Calculate the additional pressure drop value dV3 using the following equation 1;

[0022] d) Calculate the value of X using the following Equation 2; and

[0023] e) Determine the remaining battery capacity (SOC, state of charge) based on the X value:

[0024] [Equation 1]

[0025] dV3=dV2-dV1

[0026] [Equation 2]

[0027] X = dV1 - dV3

[0028] Further,

[0029] The present application provides a battery pack having a lithium-sulfur battery, comprising,

[0030] a constant current source for applying a constant current to the battery;

[0031] a measurement section for measuring a voltage and a current of the battery;

[0032] a control section for controlling the constant current source and the measurement section; and

[0033] an arithmetic section for determining a remaining capacity of the battery by calculating the voltage and the current values measured in the measurement section,

[0034] wherein, in determining the remaining capacity of the battery,

[0035] the control section applies a constant current from the constant current source to the battery in an open circuit state, and controls the measurement section to measure the voltage at any point in a range of 0.01 to 0.3 seconds after the application of the constant current and at any point in a range of 0.5 to 20 seconds after the application of the constant current, and

[0036] the arithmetic section calculates a voltage drop value dVl at any point in the range of 0.01 to 0.3 seconds and a voltage drop value dV2 at any point in the range of 0.5 to 20 seconds from the voltage measurement values, then calculates dV3 and an X value according to the following Equation 1 and Equation 2, and calculates the remaining capacity of the battery from the X value:

[0037] [Equation 1]

[0038] dV3 = dV2 - dVl

[0039] [Equation 2]

[0040] X = dVl - dV3

[0041] [Advantageous Effects]

[0042] The method for determining the remaining capacity of the lithium-sulfur battery of the present application provides the effect of reliably determining the remaining capacity of the lithium-sulfur battery in a simple manner. Specifically, even if the remaining capacity is 70% or less, the present application provides the effect of determining the remaining capacity with high accuracy.

[0043] Further, the battery pack of the present application provides the effects of expanding the application target of the lithium-sulfur battery and improving the convenience of use by implementing the above-described method. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a graph showing the relationship between OCV or operating voltage and the remaining capacity of the lithium-sulfur battery.

[0045] Figure 2is a graph showing an aspect of a change in voltage drop with time when a high output pulse (constant current) is applied at 70% or less of SOC of a lithium-sulfur battery.

[0046] Figure 3 is a graph showing a relationship of a sum of an initial voltage drop dV1 and an additional voltage drop dV3, a difference, and SOC with time when a high output pulse (constant current) is applied to a lithium-sulfur battery.

[0047] Figure 4 is a graph showing a change in voltage of a single cell with time in each SOC when a high output pulse (constant current) is applied to a lithium-sulfur battery.

[0048] Figure 5 is a graph showing a relationship between X value and SOC according to a measurement time point of an additional voltage drop value dV3 obtained by applying a high output pulse (constant current) to a lithium-sulfur battery.

[0049] Figure 6 is a graph showing a relationship between X value and SOC according to a measurement time point of an additional voltage drop value dV3 obtained according to each high output pulse by applying a high output pulse to a lithium-sulfur battery.

[0050] Figure 7 is a graph showing a relationship between X value and SOC and showing and comparing SOC fitting curves, respectively, which is obtained by applying a high output pulse (constant current, 1.0C) at each remaining capacity (SOC) of a lithium-sulfur battery, then measuring an initial voltage drop value dV1 at a time point of 0.1 seconds, and measuring a subsequent voltage drop value dV2 at a time point of 5 seconds to obtain X value.

[0051] Figure 8 An example of a battery pack according to one embodiment of the present application is schematically shown.

[0052] Figure 9 An example of estimation logic circuit of remaining capacity (SOC) according to one embodiment of the present application is schematically illustrated. DETAILED DESCRIPTION

[0053] Preferred embodiments of the present application will be described in detail below with reference to the attached drawings. Before describing the present application, it is to be noted that a detailed description of related known functions and configurations will be omitted if it is determined that its detailed description will unnecessarily obscure the gist of the present application.

[0054] The following description and drawings illustrate specific embodiments so that any person skilled in the art can easily practice the devices and methods. Other embodiments can include other structural and logical modifications. Individual components and functions can be selected and the order of processes can be changed unless explicitly stated otherwise. Parts and features of some embodiments can be included in or replaced by other embodiments.

[0055] Sulfur at the cathode of a lithium-sulfur battery is reduced in two stages upon discharging. In the first stage, sulfur (e.g., elemental sulfur) is reduced to lithium polysulfides (Li2S8, Li2S6, Li2S5, Li2S4). In the second stage, lithium polysulfides are reduced to Li2S that can be deposited on the surface of the anode. Conversely, during charging, Li2S is oxidized to lithium polysulfides (Li2S8, Li2S6, Li2S5, Li2S4), and then to lithium and sulfur.

[0056] When the state of charge (SOC) of a lithium-sulfur battery is 70%, lithium polysulfides exhibit a maximum value, after which they decrease. According to this mechanism, when the state of charge (SOC) is 70%, the electrochemical reaction of a lithium-sulfur battery changes, and as shown in FIG. 1, a lithium-sulfur battery exhibits a characteristic in which the OCV or operating voltage of the lithium-sulfur battery and the state of charge are not proportional to each other. Figure 1

[0057] Regardless of these characteristics of a lithium-sulfur battery, the inventors of the present application found a method that can reliably determine the state of charge with a simple method, thereby completing the present application.

[0058] The present application provides a method of determining the state of charge of a lithium-sulfur battery, comprising the steps of:

[0059] a) measuring an initial voltage drop value dV1 at any point in the range of 0.01 to 0.3 seconds after applying a constant current to the battery in an open circuit state;

[0060] b) measuring a subsequent voltage drop value dV2 at any point in the range of 0.5 seconds to 20 seconds after applying the constant current;

[0061] c) calculating an additional voltage drop value dV3 through Equation 1 below;

[0062] d) calculating the value of X through Equation 2 below; and

[0063] e) determining the state of charge (SOC, state of charge) of the battery according to the value of X:

[0064] [Equation 1]

[0065] dV3 = dV2 - dV1

[0066] [Equation 2]

[0067] ​X = dV1 - dV3

[0068] The inventors of the present invention have noted that when a high output pulse is applied during discharge of a lithium-sulfur battery, a pressure drop (dV1) is formed from the OCV in a very short time, and then an additional pressure drop (dV3) is slowly formed, as shown in the right graph. The reason for this phenomenon is that dV1 is significantly affected by the ionic conductivity of the electrolyte solution and the electron transfer reaction, and dV3 is significantly affected by the mass transfer resistance due to the delay of material diffusion. Figure 2

[0069] That is, due to the characteristics of the lithium-sulfur battery, the amount of leached polysulfide is the largest at 70% SOC, and at this time, the viscosity of the electrolyte solution is also the highest, so the ionic conductivity shows the lowest value. On the other hand, because the resistance is large, the initial pressure drop (dV1) is the largest when a high output pulse is applied. Thereafter, during discharge, the polysulfide is reduced to the Li2S form and solidified, the amount of polysulfide is somewhat reduced, and the initial pressure drop (dV1) tends to decrease.

[0070] On the other hand, when the SOC progresses to below 70%, the amount of reactants in the reaction solution gradually decreases, so the mass transfer resistance gradually increases due to the decrease in concentration, and thus the additional pressure drop (dV3) that is highly affected by the mass transfer resistance becomes larger and larger.

[0071] Embodiments of the present invention

[0072] Figure 3 is a graph showing the relationship of the sum of the initial pressure drop (dV1) and the additional pressure drop (dV3), the difference value, and the SOC over time when a high output pulse (constant current, 1.0C) is applied to a lithium-sulfur battery. As shown in Figure 3 When the graph shows the X value obtained by subtracting the additional pressure drop value (dV3) from the initial pressure drop value (dV1), the X value tends to continue to decrease according to the downward trend of the SOC when the SOC is 70% or less.

[0073] Therefore, according to these results, it is confirmed that the remaining capacity (SOC) of the lithium-sulfur battery can be determined from the X value.

[0074] In the method of determining the remaining capacity of the present invention, the initial pressure drop value (dV1) can be measured at any point in the range of 0.01 to 0.3 seconds after the constant current is applied, preferably in the range of 0.01 to 0.2 seconds, more preferably in the range of 0.01 to 0.1 seconds.

[0075] Figure 4 is a graph showing the change in voltage of a single cell over time in each SOC when a high output pulse (constant current) is applied to a lithium-sulfur battery. From Figure 4 ​It can be seen that if the measurement point of the initial pressure drop value (dVl) exceeds 0.3 seconds, an additional pressure drop occurs due to an increase in the mass transfer resistance, and thus, in order to the accuracy of the measurement of the remaining capacity, it is preferable to measure the initial pressure drop value (dVl) within 0.3 seconds.

[0076] In the method of determining the remaining capacity of the present application, the additional pressure drop value (dV3) can be obtained by measuring the subsequent pressure drop value (dV2) at any point within the range of 0.5 to 20 seconds after the constant current is applied and by the following Equation 1 calculation:

[0077] [Equation 1]

[0078] dV3 = dV2 - dVl

[0079] In this case, it is preferable to measure the subsequent pressure drop value dV2 within the range of 1 second to 20 seconds, and more preferably within the range of 2 seconds to 10 seconds.

[0080] Figure 5 is a graph showing the relationship between the X value according to the measurement point of dV3 and the SOC, which is obtained by applying a high output pulse (constant current, 1.0 C), then measuring the initial pressure drop value (dVl) at 0.1 seconds and the subsequent pressure drop value (dV2) within the range of 0.5 seconds to 10 seconds (in this case, the measurement point of dV3 is the same as that of dV2), obtaining the additional pressure drop value (dV3), and calculating the X value according to the following Equation 2:

[0081] [Equation 2]

[0082] X = dVl - dV3

[0083] From Figure 5 It can be seen that when the subsequent pressure drop value dV2 (or the additional charge drop value dV3) is measured within the range of 1 second to 10 seconds, the X value more corresponds to the downward trend of the SOC than when it is measured at 0.5 seconds.

[0084] In particular, it can be seen that when the subsequent pressure drop value (dV2) is measured within the range of 2 to 10 seconds, the X value more corresponds to the downward trend of the SOC.

[0085] In the method of determining the remaining capacity of the present application, it is preferable to apply a constant current of 0.5 C or more. When a constant current is applied at less than 0.5 C, it is difficult to accurately and reliably determine the remaining capacity because the pressure drop value is small, and thus, this is not preferable.

[0086] Further, it is preferable to apply a constant current of 2 C or less, and more preferably 1 C or less. When a constant current is applied exceeding 2 C, although the increase in the additional accuracy is not great, this is not preferable because a large amount of power is consumed.

[0087] Figure 6 is a graph showing a relationship between an X value of a measurement point of dV3 (a measurement point of dV2 is also the same) according to the present application and SOC, which is obtained by applying a high output pulse (constant current, 0.5C or 1.0C), then measuring an initial pressure drop value (dV1) at 0.1 seconds, and obtaining additional pressure drop values (dV3) in a range of 1 second to 10 seconds.

[0088] As shown in Figure 6 , it can be seen that the value of X well corresponds to a tendency of SOC to decrease in both cases of applying a constant current at 0.5C or 1.0C.

[0089] In the method of determining a state of charge according to the present application, the application of a constant current can be performed by a constant current generated during operation of the battery; or can be performed from a separate constant current source; or can be performed in a multiplexed manner by a constant current generated during operation of the battery and a separate constant current source.

[0090] For example, if a constant current occurs during operation of the battery, the constant current can be used, and in a portion in which a constant current does not occur during operation of the battery, a constant current can be applied by allowing different battery modules to charge / discharged from each other, or by installing a separate small capacitor to measure SOC and charge the capacitor.

[0091] Further, a constant current applied only by a separate constant current source can be used, and when a constant current is sufficiently generated during operation of the battery, only a constant current generated during operation can be used without using a separate constant current source.

[0092] Figure 7 shows a relationship between an X value and SOC, and shows an SOC fitting curve as a comparison, which is obtained by applying a high output pulse (constant current, 1.0C) at each state of charge (SOC), then measuring an initial pressure drop value (dV1) at 0.1 seconds and a subsequent pressure drop value (dV2) at 5 seconds, and obtaining additional pressure drop values (dV3) and an X value; the SOC fitting curve is obtained by approximating a normal polynomial function using a cubic function closest to the related curve.

[0093] As shown in Figure 7 , it can be seen that the X value according to SOC and the SOC fitting curve is almost the same. Therefore, the accuracy of the method of determining a state of charge according to the present application can be confirmed from this fact.

[0094] Since the chemical reaction characteristics of a lithium-sulfur battery, the method of determining a state of charge according to the present application can be preferably used when the state of charge of the battery is 70% or less.

[0095] In one embodiment of the present application, when the remaining capacity exceeds 70%, the remaining capacity of the battery is preferably determined by the open circuit voltage (OCV) value of the battery. This is because, even in the case of a lithium sulfur battery, in a range in which the remaining capacity exceeds 70%, the change value of the open circuit voltage (OCV) shows a tendency consistent with the downward tendency of the SOC, as shown in FIG. 1. Figure 1

[0096] In one embodiment of the present application, in the case of the method for determining the remaining capacity of the present application, if the remaining capacity of the battery exceeds 70%, the remaining capacity is determined by the OCV (open circuit voltage) value of the battery, and if the remaining capacity is 70% or less, the measurement of the remaining capacity can be performed in a manner determined by the X value of the present application.

[0097] Further, in one embodiment of the present application, the method for determining the remaining capacity of the present application can be performed in a manner in which a voltage method for detecting the remaining capacity of the battery by measuring the voltage of the battery; an integration method for obtaining the remaining capacity of the battery by measuring and integrating the voltage and current; or a method for supplementing the determination of the remaining capacity by using the voltage method and the integration method together.

[0098] For the voltage method for detecting the remaining capacity of the battery by measuring the voltage of the battery; the integration method for obtaining the remaining capacity of the battery by measuring and integrating the voltage and current; or the method for using the voltage method and the integration method together, a method known in the art can be used without limitation.

[0099] For example, in the case of a detection method for detecting the remaining capacity of the battery by measuring the voltage of the battery using the voltage method, the terminal voltage of the battery cell is measured, the remaining capacity is calculated based on the correlation between the voltage of the battery and the capacity (remaining capacity ratio) of the battery, for example, in a lithium sulfur battery, if the battery voltage is 2.4 V / cell, it is determined that the battery is fully charged, if the battery voltage becomes 1.8 V / cell, it can be determined that the battery is in an overcharged state, and thus, the measurement can be easily performed. However, if the voltage method is used to detect the remaining capacity during discharging, there is a problem that the detection accuracy of the remaining capacity is poor in a range in which the SOC of the battery is 70% or less, as described above. Therefore, this problem can be solved according to the method for determining the remaining capacity of the present application.

[0100] ​The integral method of obtaining the remaining capacity of the battery by measuring and integrating the voltage and current can be classified into a current integral method of measuring the current at regular time intervals and integrating the measured current, and a power integral method of measuring the voltage and current at regular time intervals, calculating the power amount by multiplying the measured voltage and the measured current, and integrating the calculated power amount. In all of the above integral methods, after the discharge current amount or the discharge power amount is calculated, the remaining capacity of the battery can be calculated from the ratio of the calculated discharge current amount or the calculated discharge power amount to the available current amount or the available power amount of the battery, which enables the remaining capacity to be stably detected without being affected by voltage fluctuations.

[0101] However, in the case of detecting the remaining capacity using the integral method, there is a problem that the detection accuracy of the remaining capacity deteriorates at the end of discharge. This is because, due to thermal loss, errors in voltage and current measurement or errors in integrated current or power are also accumulated, and a large error occurs at the end of discharge, which leads to a decrease in accuracy.

[0102] Therefore, another method of detecting the charging capacity by using the integral method and the voltage method together is used. This detection method uses the integral method from the start of charging to near full charging, and then switches the integral method to the voltage method near full charging to detect the charging capacity, and thus, the above method is able to perform measurement in the most effective region thereof.

[0103] However, in the case of the voltage method, when the current of the battery represents a small value, the calculation of its capacity provides high accuracy, while when the current represents a large value, an accurate open circuit voltage cannot be obtained due to the change in direct current impedance (Imp) in the battery or Imp depending on the ambient temperature, and thus, the capacity of the battery cannot be accurately calculated. In addition, in the case of the integral method, when the current of the battery represents a large value, the calculation of the capacity provides high accuracy, while when the current decreases, the integral error increases, and thus, the accuracy of calculating the capacity deteriorates. Therefore, the capacity of the battery can also be detected by using other methods together with the voltage method and the integral method.

[0104] In addition, in one embodiment of the present application, the method of determining the remaining capacity of the present application can be performed in such a manner that the remaining capacity value according to the X value is determined and used as a reference by previously obtaining each X value according to the remaining capacity.

[0105] In this case, the remaining capacity value according to the X value can be determined and used using the above-described various methods, and a more accurate remaining capacity value can also be determined and used by using these methods in combination.

[0106] In addition,

[0107] The present application relates to a battery pack having a lithium-sulfur battery, comprising:

[0108] a constant current source for applying a constant current to the battery;

[0109] a measurement section for measuring voltage and current of the battery;

[0110] a control section for controlling the constant current source and the measurement section; and

[0111] an arithmetic section for determining the remaining capacity of the battery by calculating the voltage and current values measured in the measurement section,

[0112] wherein, in determining the remaining capacity of the battery,

[0113] the control section applies a constant current from the constant current source to the battery in an open circuit state, and controls the measurement section to measure the voltage at any point in the range of 0.01 to 0.3 seconds after the application of the constant current and at any point in the range of 0.5 to 20 seconds after the application of the constant current, and

[0114] the arithmetic section calculates a voltage drop value dV1 at any point in the range of 0.01 to 0.3 seconds and a voltage drop value dV2 at any point in the range of 0.5 to 20 seconds from the voltage measurement values, then calculates dV3 and X values according to the following Equation 1 and the following Equation 2, and calculates the remaining capacity of the battery from the X value:

[0115] [Equation 1]

[0116] dV3 = dV2 - dV1

[0117] [Equation 2]

[0118] X = dV1 - dV3

[0119] The battery pack may, for example, have Figure 8 the shape shown. At this time, one or more than two batteries can be included, and for the constant current source, the control section, the arithmetic section, the measurement section, etc., devices known in the art can be used without limitation.

[0120] For the method of determining the remaining capacity in the battery pack, the above-described method can be applied as is.

[0121] In one embodiment of the present application, if a constant current generated during operation of the battery is available, the control section can be operated to control the constant current source to be inoperative, and the remaining capacity can be determined using the constant current generated during operation.

[0122] In one embodiment of the present application, the battery pack can be operated in such a manner that when the remaining capacity of the battery exceeds 70%, the control section prevents the constant current source from operating, and controls the measurement section to measure the open circuit voltage (OCV) value of the battery,

[0123] and when the remaining capacity of the battery exceeds 70%, the arithmetic section calculates the remaining capacity of the battery from the measured open circuit voltage (OCV) value.

[0124] In one embodiment of the present application, in the battery pack, the determination of the remaining capacity is supplemented by further performing a voltage method of detecting the remaining capacity of the battery by measuring the battery voltage, an integration method of obtaining the remaining capacity of the battery by measuring and integrating the voltage and current, or a method of using both the voltage method and the integration method.

[0125] In one embodiment of the present application, the arithmetic section of the battery pack can be operated in such a manner that by obtaining in advance an X value according to the value of the remaining capacity of the battery and data of the remaining capacity according to the X value, storing them as a reference, and comparing the X value obtained by calculation with the reference, the remaining capacity of the battery is determined.

[0126] Figure 9 An example of an estimation logic circuit of the remaining capacity (SOC) according to one embodiment of the present application is schematically shown. The operation mode of the remaining capacity (SOC) estimation logic circuit will be described as an example. Figure 9 The operation mode of the remaining capacity (SOC) estimation logic circuit will be described as an example.

[0127] First, the OCV of the battery is measured. If the OCV value exceeds 2.15 V, since the SOC exceeds 70%, the SOC is estimated using the OCV (depending on the design of the battery, the reference OCV can be slightly different from 2.15 V, and the OCV that remains constant at 70% or less of the SOC becomes the reference value, rather than fixing the OCV at 2.15 V).

[0128] In this case, the SOC can of course be estimated by the various methods described above.

[0129] On the other hand, when the OCV value is 2.15 V or less, since the SOC is 70% or less, a high current pulse (constant current) is applied to measure the initial voltage drop dVl and the subsequent voltage drop dV2, and dV3 and the X value are obtained, thereby estimating the SOC value.

[0130] In this case, the estimation of the SOC value is performed in such a manner that the SOC value is calculated by obtaining in advance and storing in a database, and comparing the X value for each SOC with the X value obtained as above.

[0131] In this case, the SOC value calculated as above can be supplemented by a voltage method of detecting the remaining capacity of the battery by measuring the voltage of the battery as described above; an integration method of obtaining the remaining capacity of the battery by measuring and integrating the voltage and current; or a method of using the voltage method and the integration method together.

[0132] 2.15 V used as the above OCV value is a typical OCV value of a lithium-sulfur battery, which can vary depending on individual characteristics of various types of lithium-sulfur batteries.

[0133] Although the present application has been described with respect to the preferred embodiments, various modifications and changes can be made without departing from the spirit and scope of the application. Accordingly, the appended claims shall cover these modifications and changes, provided they fall within the scope of the application.

Claims

1. A method for determining the remaining capacity of a lithium-sulfur battery, comprising the following steps: a) After applying a constant current to the battery in an open-circuit state, measure the initial voltage drop dV1 at any point within the range of 0.01 to 0.3 seconds; b) After the constant current is applied, measure the subsequent voltage drop dV2 at any point within the range of 0.5 seconds to 20 seconds; c) Calculate the additional pressure drop value dV3 using the following equation 1; d) Calculate the value of X using the following Equation 2; and e) Determine the remaining capacity (SOC, state of charge) of the battery based on the X value: [Equation 1] dV3=dV2-dV1 [Equation 2] X = dV1 - dV3.

2. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 1, wherein, The constant current is applied at a temperature between 0.5C and 2.0C.

3. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 1, wherein, The application of the constant current can be performed by a constant current generated during the operation of the battery; or it can be performed from a separate constant current source. Alternatively, it can be performed in combination with the constant current generated during the operation of the battery and the separate constant current source.

4. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 1, wherein, The method is applied when the remaining capacity of the battery is below 70%.

5. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 3, wherein, When the remaining capacity of the battery exceeds 70%, the remaining capacity of the battery is determined by the open circuit voltage (OCV) value of the battery.

6. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 1, wherein, The method determines the remaining capacity, and supplements the determination of the remaining capacity by the following methods: a voltage method for detecting the remaining capacity of the battery by measuring the voltage of the battery; and an integral method for obtaining the remaining capacity of the battery by measuring and integrating the voltage and current. Alternatively, the voltage method and the integration method can be used together.

7. The method for determining the remaining capacity of a lithium-sulfur battery according to claim 1, wherein, The remaining capacity of the battery is determined by obtaining each X value in advance based on the remaining capacity and using each X value as a reference.

8. A battery pack having a lithium-sulfur battery, comprising, A constant current source, wherein the constant current source is used to apply a constant current to the battery; A measuring unit, the measuring unit being used to measure the voltage and current of the battery; The control unit is used to control the constant current source and the measuring unit; as well as An arithmetic unit is used to determine the remaining capacity of the battery by calculating the voltage and current values ​​measured in the measuring unit. Among them, when determining the remaining capacity of the battery, The control unit applies a constant current from the constant current source to the battery in an open-circuit state, and controls the measuring unit to measure the voltage at any point within a range of 0.01 to 0.3 seconds after the application of the constant current and at any point within a range of 0.5 to 20 seconds after the application of the constant current. The arithmetic unit calculates the voltage drop value dV1 at any point within the range of 0.01 to 0.3 seconds and the voltage drop value dV2 at any point within the range of 0.5 to 20 seconds based on the voltage measurement value. Then, it calculates dV3 and the X value according to the following Equations 1 and 2, and calculates the remaining capacity of the battery based on the X value: [Equation 1] dV3=dV2-dV1 [Equation 2] X = dV1 - dV3.

9. The battery pack according to claim 8, wherein, When the constant current generated during the operation of the battery is available, the control unit controls the constant current source to not operate.

10. The battery pack according to claim 8, wherein, If the remaining capacity of the battery exceeds 70%, the control unit prevents the constant current source from operating and controls the measurement unit to measure the open-circuit voltage (OCV) value of the battery. If the remaining capacity of the battery exceeds 70%, the arithmetic unit calculates the remaining capacity of the battery based on the measured open-circuit voltage (OCV) value.

11. The battery pack according to claim 8, wherein, The battery pack further supplements the determination of its remaining capacity by performing the following methods: a voltage method for detecting the remaining capacity of the battery by measuring the voltage of the battery; and an integral method for obtaining the remaining capacity of the battery by measuring and integrating the voltage and current. Alternatively, the voltage method and the integration method can be used together.

12. The battery pack according to claim 8, wherein, The arithmetic unit determines the remaining capacity of the battery by pre-obtaining the X value based on the remaining capacity of the battery and the data of the remaining capacity based on the X value, storing the X value and the data as a reference, and comparing the calculated X value with the reference.

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